The changes involve how users view the status updates and shared items from their Facebook network. The most important updates will now appear in the "News Feed," but users can toggle to "View Live Feed" to view all status updates.

Additionally, photo tagging, friend acceptances, RSVPs and the like will be moved back into the main feed in the middle column. Several of these currently appear in the right column.

As for why Facebook was changing the homepage again, they gave a vague answer:

Some of you may ask why we are changing the home page again. Like you, we know it can be disruptive when things are moved around, but we hope that these changes make Facebook a more valuable experience for you. We put a lot of thought into all the changes we make to the site and do a lot of testing before releasing anything.